Quote:
Originally Posted by whitevette
I used to be a 20-W-50 freak...then I got smart. Hot 50 wt is thin, cold 20 wt is like glue on crank-up. This is when your (cold) engine really needs oil protection ... visualize rings scrapping on cold steel walls. Cold oils are not gonna "sling" easily from spinning rod big ends.
Then, I spoke with a Pennzoil rep. Most of the wear occurs cold. The oil is still drained down from the overnight sit... it started this sit duration hot ( engine soak) , so the oil was super hot ( and thin) and drained down from
everywhere ( except from the very close rod & main clearances).
You come out in the (cool?cold?) AM, turn the key, and wham! Things start happening. No oil things. Bad.... 20-W-50 bad. Like I said...I USED to be....
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I'm of the opposite school of thought. A thin oil may "pump up" faster, but I don't think it'll hold as good of pressure when cold. Being a truck driver, sometimes my motor gets beat on pretty hard when cold, hot, whatever.
And I'm not convinced a thin oil will pump up measureably faster than a thick one. My oil pump is a positive displacement pump. It's spun by the engine. It's going to move the oil. Non-negotiable.
And by cold starts, I mean 40 or 50 F block temperatures. Rarely, somewhere in the ballpark of 30. That, to me, is a cold start. 20wt is still plenty pumpable at 30 F.
But you're right. Based on my oil pressure gauge observations, 20w-40 or even straight 30 wt may be better.